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IGCSEBiology
Trial Class

Original practice · 5 questions · 15 marks · about 17 minutes

Water and Ions in Biology Practice Questions

Biology editorial review is supported by the named review panel. Reviewer participation may vary by guide. Checked against Cambridge IGCSE Biology 0610 (2026–2028); last reviewed August 2026.

These questions cover the importance of water as a solvent, the roles of key mineral ions in plants and animals, and how deficiencies affect organisms.

Before you open the answers

  • Attempt every question without notes.
  • Show working for calculations and write complete biological statements.
  • Use the suggested time as a guide, not a strict limit on the first attempt.

These are original practice questions. They do not reproduce an official Cambridge paper or official mark scheme.

  1. Question 1

    Paper 2 Both 3 marks Difficulty 2/5

    State three roles of water in the human body.

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    1. Solvent for chemical reactions / metabolic reactions take place in solution.
    2. Transport medium: carries dissolved substances in blood plasma.
    3. Temperature regulation: evaporation of sweat cools the body.

  2. Question 2

    Paper 4 Extended 4 marks Difficulty 3/5

    State the role of each of the following ions in plants and describe the effect of a deficiency: (a) nitrate ions, (b) magnesium ions.

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    1. (a) Nitrate ions are needed to make amino acids / proteins for growth.
    2. Deficiency causes stunted growth / yellow older leaves.
    3. (b) Magnesium ions are needed to make chlorophyll.
    4. Deficiency causes yellow leaves / chlorosis: reduced photosynthesis.

  3. Question 3

    Paper 2 Core 2 marks Difficulty 1/5

    Name the mineral ion needed to make haemoglobin and state the effect of its deficiency.

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    1. Iron.
    2. Deficiency causes anaemia: fewer / less effective red blood cells, tiredness, weakness.

  4. Question 4

    Paper 4 Extended 3 marks Difficulty 4/5

    A farmer notices that their crop plants have yellowing leaves despite receiving plenty of water and sunlight. Suggest which mineral ion may be deficient and explain your reasoning.

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    1. Magnesium deficiency (or nitrogen deficiency).
    2. Magnesium is needed to make chlorophyll: without it, leaves turn yellow (chlorosis).
    3. Even with adequate light and water, photosynthesis is reduced without chlorophyll.

  5. Question 5

    Paper 4 Extended 3 marks Difficulty 3/5

    Explain why water is described as a "good solvent" and why this property is important for living organisms.

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    1. Many substances dissolve in water (it is polar): salts, sugars, amino acids.
    2. Dissolved substances can be transported around the body (in blood plasma, in xylem sap).
    3. Chemical reactions in cells occur in aqueous solution: metabolism depends on water as a medium.

Mark the set consistently

Award a point only when the idea is clearly present in the written answer. Correct any missed point in a complete sentence, then test the same skill on a different question several days later.

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